Geographic Range

Lates niloticus (Nile perch) is widespread throughout the Ethiopian Region of Africa, occurring commonly in all major river basins including Nile, Chad, Niger, Senegal and Volta. The nilotic population penetrates northwards well into the geographical limits of the Mediterranean Region and is present in the waters of Lake Mariout situated in the Nile Delta. Southwards the distribution includes parts of the Congo Basin. The most common place to find the Nile perch is in Lake Victoria where the species was introduced in 1962. (Hopson, 1972)

Habitat

Nile perch are found in many different types of fresh water. They prefer warm, tropical waters (27°N – 7°S) where they grow to large sizes and occur in high densities. Adult Nile perch occupy all habitats in lakes and rivers (10-60 m in depth) where there is enough oxygen with the exception of rocks, swamps, and the pelagic zone. Small juveniles are restricted to shallow near-shore environments (Luna, 2002; Queensland Government, 2002). (FishBase, 2004; Queensland Department of Primary Industries and Fisheries, 2004)

Physical Description

Nile perch are silver in color with a blue tinge. They have a distinctive dark black eye with a bright yellow outer ring. Nile perch are usually seen around 2-4 kg, but have been caught and seen at sizes up to 200 kg (the largest at 232 kg). They average around 85-100 cm but can grow to 193 cm. The females are generally larger than males. The preopercle and pre-orbital bones are armed with spines, with a large spine on the free edge of the operculum. (FishBase, 2004; Queensland Department of Primary Industries and Fisheries, 2004)

Development

The growth of the Nile perch is very fast during the first year. The rate then decreases during the second, third, fourth and fifth years. (Acere, 1984)

Reproduction

Nile perch are sexually dimorphic. The male has only anal and urogential openings just anterior to the anal fin, whereas the female has a genital orifice separate from the urinary opening. They become sexually mature at the age of 3 years. Males dominate the sex ratio up to 80 cm TL, while the females are dominate at 80 cm TL and above (Asila and Ogari, 1988). Ovulation takes place in the spring with the rising water temperature. Spawning is usually done in sheltered areas, but can also occur in open waters. (Hopson, 1972)

Behavior

Communication and Perception

Food Habits

The diet of Nile perch consists of fishes, insects, crustacea and mollusks. The type of prey ingested by the predator depends on the predator size, prey availability and abundance within a given habitat (Ogari, 1984). Juvenile Nile perch feed on copepods, prawns in the genus Caridina, fish fry, small gastropods, and bivalves. As the fish matures and moves to greater depths haplochromine cichlids constitute over 95% of their food consumption. Occasional items found in the Nile perch's diet include smaller fish in the genera Barbus, Clarias, Haplochromis, Lates, Oreichromis, and Xenoclarias. Besides crustacean zooplankton, invertebrate prey includes snails, clams, and insects (odonate larvae, aquatic Hemiptera, mayflies in the genus Povilla, and larvae of phantom midges (Chaoborus). Fish in the genus Rastrineobola are very common in the diet in terms of occurrence, and are second to haplochromines (Acere, 1985). As Nile perch grow larger, they take larger prey. Nile perch less than 80 cm tend to feed on smaller fishes than those greater than 80 cm. This demonstrates that the predator is capable of shifting to other sizes of prey when more suitable sizes become scarce (Ogutu-Ohwayo, 1984). (Acere, 1984; Ogari, 1984; Ogutu-Ohwayo, 1984)

Ecosystem Roles

The Nile perch acts as a major predator in its native and introduced habitats.

Nile perch have been observed with several different kinds of parasites, Lernea (region after the operculum), arguilids (in the gills), and various nematodes (throughout the body). (Acere, 1984)

Economic Importance for Humans: Positive

The Nile perch has yielded an increase in total fishery, and fishery-related employment has increased dramatically. Since the increase of Nile perch, larger factory fishing companies have thrived greatly. (Kitchel and Schindler, 1997)

Economic Importance for Humans: Negative

The introduction of the Nile Perch to Lake Victoria has caused serious ecological problems. The richness and diversity of endemic cichlid species is rapidly declining. Over 300 native species have already been driven to extinction due to the feeding patterns of the Nile perch (Schofield, 1999). Although for the time being the strong increase of L. niloticus seems to be a favorable development for the fishing industry, the final consequences may be very serious for future fish production in the lake (Goudswaard and Witte, 1984). Since the increase of Nile perch, the accelerated decline in diversity has altered the food web structure and caused ecological changes due largely to human actions, which have profound socioeconomic effects (Kitchell and Schindler, 1997). The continuing degradation of Lake Victoria's ecological functions has serious long-term consequences for the ecosystem services it provides and may threaten social welfare in the different countries bordering its shores (Verschuren and Johnson, 2002). Also since the increase of Nile perch, smaller scale fishing companies have been hurt significantly. (Goudswaard and Witte, 1984; Kitchel and Schindler, 1997; Schofield, 1999; Verschuren and Johnson, 2002)

Conservation Status

Contributors

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

introduced

referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

Acere, T. 1984. Observations on the biology, age, growth, maturity and sexuality of Nile perch, *Lates niloticus* (Linne), and the growth of its fishery in the northern waters of Lake Victoria. FAO Fisheries Report, 335: 42-61.

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This material is based upon work supported by the
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Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.